During emergencies, typically fires, it becomes often necessary to rapidly evacuate persons from the affected structure such as a highrise building (hereinafter simply referred to as "building"). This can become difficult, dangerous and impossible if access to the internal fire escapes is blocked; for example, by flames and smoke. In such cases the only available escape route may be along the exterior of the building, but ordinarily that route is, under the best of circumstances, available to only the occupants of the lowest floor or floors of the building.
While floors at intermediate heights of the building could be evacuated via ladders, provided they are available at all, occupants of the higher floors are in great danger unless the fire can be controlled in time before it reaches and/or spreads throughout such floors.
Thus, attempts have been made in the past to provide occupants of buildings with a way to escape along the exterior of the building during emergencies. Typically, this involved providing a rope or cable that is suitably anchored to the building, a mechanism frictionally engaging the rope and adapted to suspend the escaping person therefrom, and means operable by the escaping person for controlling friction to thereby lower himself at a controlled, sufficiently low speed to prevent injury upon the person's arrival on the ground. Exemplary of prior art efforts for escaping along the exterior of buildings are U.S. Pat. Nos. 5,145,036; 4,934,484; 4,705,142; 4,679,654; 1,190,389; and 702,858.
The prior art devices have a number of drawbacks, including their reliance on power from the person descending to slow the rate of descent, their need for some skill on the part of the descending person to properly operate it, and their inability for an efficient and quick reuse by several persons requiring evacuation because the devices are typically limited for use by one person only. They are therefore more suitable for individual escape mechanisms, adapted to be carried around by the intended user, but not well suited for permanent installation at various building sites as a standby to quickly evacuate several persons if and when an emergency arises.
From operational and safety points of view, it would of course be preferred if buildings could be fitted with escape devices which, on demand, automatically lower a person at a safe, controlled speed along the exterior of buildings without relying on the strength, dexterity, skill or, indeed, consciousness of the person being lowered. Such devices could be powered by electric motors, and appropriate mechanical, electromechanical and/or electronic controls are available to operate the devices. The problem with this approach is that in emergencies it is possible, indeed it is to be expected, that no power is available. Hence, power-driven escape devices are not feasible because the likelihood that they will be inoperative is greatest at the very moment when they are needed.
Accordingly, there is presently a need for a self-contained device which, without the need for external power and/or personal strength and skill, can lower persons during emergencies from the building to the surrounding ground at a controlled, safe speed at which injuries due to impact with the ground are prevented.